Plastics colouration

Abstract

A method of imparting color to a plastic substrate comprising applying to the substrate, or incorporating within the substrate, a diacetylene compound of general formula (I) wherein n=1 to 20; R 1 =an optionally substituted C 1-20 alkyl group which may contain heteroatoms; T=H, an optionally substituted C 1-20 alkyl group which may contain heteroatoms or —(CH 2 ) m —C(═O)-Q 2 R 2 ; Q 1 =NH, CO, NHCONH, OCONH, COS, NHCSNH or NR 3 , wherein m, Q 2 and R 2 are independently selected from the same groups as n, Q 1 and R 1 respectively; R 3 is an optionally substituted C 1-20 alkyl group which may contain heteroatoms; and irradiating the substrate to impart color to the substrate is described.

The invention claimed is: 
     
       1. A method of imparting colour to a plastic substrate, wherein the plastic substrate is selected from packaging, product wrapping films, and melt spun fibres, wherein the plastic substrate is polycaprolactone (PCL) or low density polyethylene (LDPE), wherein said method comprises applying to the substrate, or incorporating within the substrate, a diacetylene compound of general formula (I)
   R 1 Q 1 -C(═O)—(CH 2 ) n —CΞC—CΞC—(CH 2 ) n —C(═O)-Q 1 R 1   (I)
 
 wherein 
 n =1 to 20; 
 Q 1 =NH or NR 3 , 
 R 3  is an optionally substituted C 1-20  alkyl group which may contain heteroatoms; and irradiating the substrate to impart colour to the substrate; 
 wherein R 1  is a saturated aliphatic hydrocarbon group having a chain length of 8 to 20 carbon atoms, 
 wherein the diacetylene compound is initially applied to the plastic substrate or incorporated within the plastic substrate in an inactive form, and is subsequently activated by an activating stimulus, prior to being irradiated to impart colour to the plastic substrate, 
 wherein the activating stimulus is selected from heat at a temperature about or above the melting point of the diacetylene compound and near-infrared light in a wavelength range of 700 nm to 2500 nm, and 
 wherein, when the activating stimulus is near-infrared light, the plastic substrate further comprises a near-infrared light absorbing agent. 
 
     
     
       2. The method according to  claim 1 , wherein Q 1  is NH. 
     
     
       3. The method according to  claim 1 , wherein n=8. 
     
     
       4. The method according to  claim 1 , wherein the plastic substrate is irradiated with light in the wavelength range 200 to 450 nm to impart colour to the substrate. 
     
     
       5. The method according to  claim 1 , wherein the plastic substrate further comprises a light absorbing agent. 
     
     
       6. The method according to  claim 1 , wherein the diacetylene compound is incorporated into the plastic substrate when the plastic substrate is in molten form. 
     
     
       7. The method according to  claim 1 , wherein the diacetylene compound of general formula (I) is selected from:
 10,12-docosadiyn-bis-n-octylamide, 
 10,12-docosadiyn-bis-n-decylamide, 
 10,12, docosadiyn-bis-n-tetradecylamide, 
 10,12-docosadiyn-bis-n-hexadecylamide, and 
 10,12-docosadiyn-bis-n-octadecylamide. 
 
     
     
       8. The method according to  claim 1 , wherein R 1  is a saturated aliphatic hydrocarbon group having a chain length of 8, 10, 12, 14, 16, 18, or 20 carbon atoms. 
     
     
       9. The method according to  claim 1 , wherein the plastic substrate is PCL. 
     
     
       10. The method according to  claim 1 , wherein the plastic substrate is LDPE. 
     
     
       11. The method according to  claim 1 , wherein the activating stimulus is heat at a temperature about or above the melting point of the diacetylene compound. 
     
     
       12. The method according to  claim 1 , wherein the activating stimulus is near-infrared light and the plastic substrate further comprises the near-infrared light absorbing agent.